DE 10 2012 201 567 A1 shows a central valve of a camshaft adjuster of this type. The inflow takes place via a radial bore in the camshaft and supplies the central valve with pressure medium via its camshaft-side end. The outflow takes place via a radial bore on the valve housing. For the purpose of control, the central valve has two supply ports, with the aid of which a connection may be established between an inlet port and a working chamber of the camshaft adjuster. Refinements of camshaft adjusters of this type include additional features, for example a locking piston, which is able to mechanically fix the moving elements of the adjuster. Another supply port and an additional switching position are necessary—i.e., an extension of the central valve, with the aid of which the locking piston may be driven. One disadvantage is the elongation of the control valve following a conventional extension, which affects the required installation space.